Method and machine for file grinding



Sept. 30, 1930. H. L.. BAlLEY METHOD AND MACHINE FOR FILE GRINDING 7Sheets-Sheet Filed March 14, 1925 Jhderdo HEREERT L. @AQLEY LWKMS Sept.3 1930- H. BAILEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14,1925 7 Sheets-Sheet 2 Men/01:-

HERBERT' LBABLEY I Sept. 30, 1930. L BAlLEY I 1,777,135

METHOD AND MACHINE FOR FILE GRINDING mam? Baum 7 Sheets-Sheet 4 I. IIII/denier HERBERT L.BAILE j MflOrmQV" H. L BAILEY METHOD AND MACHINEFOR FILE GRINDING Filed March 14 Sept. 3@, 1930.

Sept. 30, 1930.

H. L. BAILEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14 1925 7Sheets-Sheet 5 \lllJ llllllll G 5 w M6 i .7 1 wwfiw 7 5 5 w m 9 .V.. wwM;fi /2,22 wm z... .2222%,,25,2 .r i... n M a 4% 5 I 5 G B G a m m B m HInventor- HERBERT L. BAILEY Sept. 30, 1930.

H. LuBAlLEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14, 1925 7Sheets-Sheet 6 FIG 7 Sheets-Sheet H. L. BAILEY METHOD AND MACHINE FORFILE GRINDING Filed March 14 FIG. 22

5ept. 30, 1930.

ATTORNEY.

R. 0 Y T 7 WA 5 L T R E 5 R E H FIG. 24

I/MIIIII'IIIII e I FIG. 25

Patented Sept. 30, 1930 PATENT OFFICE HERBERT L. BAILEY, OFPHILADELPHIA, PENNSYLVANIA METHOD AND MACHINE FOR FILE GRINDINGApplication filed March 14, 1925. Serial No. 15,592.

My invention relates to file grinding machines. The machine which I havedesigned is especially adapted for the grinding of files, the teeth ofwhich are machine-cut and 5 are of a substantial and uniform distanceapart. Such files are known as cutting files rather than abrading filesinasmuch as the teeth are sharpened in such fashion that each'one ofthem shaves or cuts the surface of the metal in a regular manner asdistinguished from the irregular scratching and abrading action of theordinary file. These files are commonly made by special millingprocesses and are very expensive. By my invention I am enabled tosharpen the edges of these teeth when'they are dulled a number ofdifferent times whereby the life of the file is greatly prolonged, andthe great expense of new files hitherto incident to the dulling of theteeth is eliminated. These tools can now be used with great economy.

.The general object of my invention is the production of a machine whichwill effectually sharpen these cutting files. Ef-

fectual sharpening requires not only that the edge be shar but also twoother important things. irst, that the cutting angle of the edge becorrect, otherwise the file will not take hold upon the work, and,secondly, that the cutting edges of all the teeth of a given file lie inthe same eometric plane, or in the same geometric sur ace upon whichthey were originally designed to lie. Otherwise the teeth will cutunequally and the file will soon be dulled in spots and become quiteuseless.

My object is principally to produce such a machine which will grindthese files automatically without any special attention on the part ofan operator once the initial adjustment for the first file to be groundhas been made, and once any file has been inserted into a machine soadjusted. This requires not only automatic but very 1ntimate relationbetween grinding tool, workholding and work-feeding mechanisms.

It is a further principal object of my inventionto provide for the readyadjustment of the machine as a Whole and all its automatic features toaccommodate not only files of different sizes and spacings of teeth, butalso files of different makes and types, and general variation inconfiguration. Such adjustments are necessarily multiple in characterand of both a major and minor nature, and effect in common the grinding,work-holding and feeding mechanisms.

In a kindred line I aim also to provide those exacting adjustments whichenable me to accomplish in connection with these various kinds of filesthat same effectual grinding which I have outlined above as the primaryobject of my invention, to repeat.a

sharp edge on each tooth, a proper angle to each face, and a properalignment of the edges of all the teeth in the geometrical surface whichthey should occupy. Beyond this I aim to make the adjustments such thatthere shall be provided on each tooth a let off at each end sulficientto prevent scratching which might accompany the presence of asharpcorner or point. For it must be remembered that the particular work ofexterior finishing upon which files of this class aroused will not admitof scratches in the surface of the body being finished.

In accomplishing my aims I have invented an entirely new method ofgrinding, a method involving a considerable number of steps. To beginwith, I establish the oint of greatest depth of the grinding to t e rearof the tooth edge and traverse this point of greatest depth on a pathparallel to the tooth edge. This insures uniform edge on the tooth andlong life to the work. Another step involves the holding of the work tothe grinding tool by yielding pressure insufficient to hold the Work inits initial position. This adds to the preceding advantages theadvantage of a let- Qfi' at each end of each tooth whereby the0bjectionable sharp corners aforementioned are eliminated. Yet anotherstep comprises the relative movement of the work and the grinding toolon a zig-zag path taking in alternate teeth on corresponding branches ofthe path, whereby there results further uniformity of cutting edge,adherence to cutting surface, and lllgll speed of operation. A stillfurther step is the gravitational balance of the work during thegrinding operation, whereby the displacement of the work, due tounwonted grav tational components, which may vary as the work is belngfedfrom one position to another, is entirely obviated. An ancilliarystep is the application of all holding and feeding forces symmetricallywith reimproved means for feeding the work so held,

and likewise improved means foradjusting the work and the grinding tool,and the Various parts having to do with them, all in such fashion asbest to practice the method which I have evolved.

In the accompanying drawings, I have shown that embodiment of myinvention now best known to me.

' Of these drawings,

Fig. 1 is a general sideelevation of the entire machine.

Fig. 1--A is a similar side elevation of the entire machine from theside opposite that of Fig. 1. i

Fig. 2 a substantially longitudinal central vertical section. Itresembles Fig. 1 except for the sectional showings and the omission of adriving motor. I

Fig. 3 is a top plan view of the machine.

Fig. 4-is a transverse section on the zigzag line 44 of Fig. 2. a

Fig. 5 is an end elevation of the workholding end of the machine.

Figs. 6 and 7 are, respectively, plan views partiallyin section of thefriction clamp of the work-holding means.

Figs. 8 and 9 are, respectively, front elevations of two different formsof this clamp.

Fig.1'0 is a section on the line 101O of Fig. 2 showing salient elementsof the workfeeding mechanism.

Fig. 11 is a semi-diagrammatic view showing other salient features ofthe mechanism and method of feeding.

Fig. 12 is aview of the portion of the drive of the feeding and grindingmechanisms taken substantially on line 12-12 of Fig. 3 looking in thedirection of the arrows and showing in full lines parts shown in dottedlines in Fig. 1. i

Fig. 13 is an elevation partially in section of one form of operatingmechanism for the grinding tool, the sectional portion of the figurebeing taken substantially on line 1313 of Fig. 3.

Fig. 14 is a plan view of this mechanism with certain of the drivingelements opened apart.

Fig. 15 is a side elevation of a modified form of grindingtool'operating mechanism.

Figs. 16 to 21 are diagrammatic views having to do with the explanationof the method of my invention.

Fig. 22 is'a section showin certain gearing of the driving mechanismtaEen substantially on line 22-22 of Fig. 1.

Fig. 23 is an enlargement of a micrometer adj ustment shown in FigureFig. 24 is a vertical section of the fore end In the machine I havedeveloped to carry.

out the method of my invention, the main driving mechanism for thewhole,the grinding tool operating mechanism, the work-holding mechanism,the work-feeding mechanism, and the adjusting mechanisms have beencoordinated and combined together into a highly efiicient whole. In thedrawings, the main driving mechanism is by the letter. D, themech'anismfor operating the grinding tool is desi 'nated by t e letter G, thework-holding mechanism by the letter H, the work-feeding mechanism bythe letter F applied to its salient elements, and the adjustingmechanism at large by the letter A. Coordination of the work-holding,feeding and adjusting mechanisms brings them into a simplified unitarygroup structure as clearly 1 appears in Figs. 1 and 4, exce t thatrelated portions of the feeding and ad usting mechanisms are embodied inthe same structure with the main driving mechanism D, as indicated bycorresponding group designating letters in the bod of group D. The wholeis supported rom a pedestal P which stands upon an extended horizontalbase S.

The base S comprises the main body 30 of considerable width and arelatively narrower portion 31 upon which the pedestal P is mounted. Thepedestal itself is provided with a head 32 lying in a substaniallyhorizontal plane. Swiveled to it by a central securing bolt 33 by means.of which-it may be clam ed and unclamped to the head, and angular yadjusted upon the'head, is a stirrup 34, u on which the main drivecasing 35 of the driving mechanism D is supported from the pedestal. Thestirrup 34 is preferably integrally formed with and depends from thebottom of the fore end of this casing 35. The casing 35 is box-like inform,

as clearly appears from Fig. 2, a view in. which its interior is shownby removing its front side 36. The side 36 is purposely made removablefor the urpose of rendering accessible the parts 0 the main drivingmechadesignated generally lo'u lzio

nism enclosed within the casing. The side 36 is provided with hinges 37at its rear end permitting it to swing outwardly, but it is normallysecured in place by securing bolts,

38, applied to the corners or to other con venient points. Thelubrication and protection of the parts of the driving mechanism withinthe casing, 35, are properly assured by its normal closure. From therear end of the motor casing depends the bracket or spider, 39, to whichthe driving motor, 40. is attached in-a vertical position by means ofany appropriate securing 'means. This driving motor has avertically-extending main driving shaft, 41, from which all of themechanisms of the machine requiring power to drive them are driven. Thevertical shaft,

41, is appropriately journaled in upper and I means of a bracketstructure 44. From the lateral branches of the stirrup 34 theworkholding, feeding and adjusting mechanisms H, F, and A, are supportedlargely in position laterally of the grinding mechanism G.

- This support is by means ofa laterally projecting arm socketed in alateral extension 46 from the front branch ofstirrup 34, and avertically-extending column 47 mounted pivotally thereon, as indicatedgenerally at The elements of the driving mechanism per se other than thedriving motor 40 and its drive shaft 41 will be best comprehended asdescribed in connection with the particular ones of the other mechanismwith which suitable type, such as is well known in the art, by means ofan upwardly-extended shaft 51 upon which it is mounted. A pulley 52 onthe shaft 51 is driven by a belt 53 which I connects it to a drivingpulley 54 on theupper end of the main drive shaft 41 so the grindingtool is rotated at.the high speed required. A belt-tightening idler 55carried at the upper end of depending crank arm 56 is mounted forvertical and angular adjustment in an oscillatable and adjustablepedestal 57, and spring-pressed to the belt 53 by the spiral spring 58having one end bearing on the casing 35 and the other end engaging thepedestal 57.

Grinding wheel 49 of the mechanism G is supported in an inclinedtransverse plane, as clearly appears in Figs. 1 and 2, by means of anarm 59 associated with the bracket 44 by which the mechanism at largeissupported. Arm 59 carries the grinding tool by meansof a split collar60 adj ustably clamped around the bearing 50 of the grinding tool bymeans of screw 61 (see Fig. 13), whereby the grinding tool may be freelyadjusted vertically merely by loosening clamping member 60 and movingthe bearing longitudinally therethrough. But the arm 59 is not fixedlyconnected to the bracket 44. It is mounted (see Figs. 13 and 14particularly) on a sliding head 62 carried upon a transverse shaft 63.This shaft 63in turn is supported in depending cars 64 in a grindingmechanism supporting frame 65 carried from the bracket 44 on the upperside of the casing 35. Support is by means of a tubular boss 66telescoped over the tubular forwardly and substantially horizontallyextending end 67 of bracket 44. It is adjustably held in this relationby means of set screw 68, through the release of which it may be movedangularly about the axis of extension 67 and reset in a differentangular position whereby the obliquity of the plane in which grindingtool 49 operates may be set to any desired angle.

- Immediately overlying the transverse shaft 63, the head 62. isprovided with a rack 69. This rack is engagedby a pinion 70 on the'endof a shaft 71 journaled interiorly of bracket 44 and its with the"tubular extension 67. The opposite end of shaft 71 projects rearwardlyfree of bracket 44 (Figs. 1 to 3) and is there provided with beveledgear 72 meshing with a like gear 73 on the upper end of a shaft 74 boss66 and co-axially extending substantially vertically down through thetop of casing 35. On its lower end this shaft 74 is provided with asecond beveledgear 75 which in turn meshes with the segmental beveledgear 7 6 carried by a horizontally extending stub shaft 77 secured tothe cover plate 36 of the casing 35. This segmental gear 76 (see Figs. 1and 12) is provided with a rocking arm 78 having a pin and slotconnection 79 of an adjustable nature with the rocking link 80 connectedin turn at its opposite end adjustably with the side of a rotatable cam81 mounted on a second stub shaft 82, also secured on the cover or door36 ofthe casing 35. This cam 81 is in turn coupled with a worm gear 83(see Figs. 1 and 22) having, a driving engagement with thevertically-extending worm 84 carried by the vertically-extending drivingshaft 85 journaled in the top and bottom walls of the casing 35intermediate the side walls thereof. This shaft is driven by belt 86from the main drive shaft 41, the speed D grindin mechanism G isoperated and grinding w eel 49 reciprocated laterally in a determinatepath,

The work-holding mechanism H comprises, in the main, a friction clamp 89adapted to frictionally hold the work, as for example the file 90, inposition before the grinding tool 49. This friction clamp, when theFparts are in operating position, as shown in igure 2, supports the workin a substantially verticai position, asclose to the vertical asposible, so that the work is gravitationally balanced about an axialline, such as 91. The clamp is supported from an inwardly extending arm92 connected with the upper end of column 47 which in turn, it will beremembered, is supported by the horizontally extending arm 45 socketedin stirmp 34. The clamp comprises a head plate 93 carried upon theheaded ends 94 of bolts 95 projected, respectively, through the tubularends 96 of a bracket 97, centrally mounted upon a circular shaft 98carried in the upper end of the forwardly-extended arm 92. Shaft '98 isadjustably carried on arm 92 by virtue of its passa e through thecomplemental bearing member 99, and its retension therein in adjustedposition by means of the winged adjusting screw 100. Similarly, bracket97 is supported upon shaft 98 by a complemental bearing 101 and held in'its adjusted position by a winged adjusting nut 102, and the head 93 isretained upon the bracket by wing nuts 103 on the ends of the bolts 95.

This head 93 of the friction clamp is provided with a pair of front jaws104 of angle form in transverse section having branches 105 which rojecttoward each other in spaced relation to the head 93 and other brancheswhich extend toward the head 93 and are secured to complemental branchesof angle slides 106. These slides are slotted, as at 107 (see Figs. 8and 9) and are retained in place by the heads 94 of the clamp headsecuring bolts 95, the bodies of which are passed through the slots.Moreover, the clamp head 93 is provided with slots 107 Fig. 5-inregistry with the slots in the members106, and members 106, at theirinner edges, are provided with lugs 108 which pro- Lect into the slotsin the clamp head 93 where- -y swinging movement of members 106 aboutthe bolts 95 is precluded, and the jaws 104 are maintained in theirvertically aligned position. Yet the provision of slots 107 and 107permits of a considerable range of lateral adjustment of the head plate93 bodily, and of the clamping jlaws 104 in particular, merely byloosening of the wing nuts 103 which free the parts from the bindingaction of hqeads 94, which secure them to the bracket 9 The jaws 104 areadapted to' engage the front face of the work by the overhanging 109,may be easily removed for the renewal of the surfaces or the replacementof the jaws by others. The work is borne to these work-engaged interiorfaces 109 by means ofa rear clampin jaw 111 in the form of a headprojected t rough an aperture 112 in the clamping head 93 from the rearby a spring-pressed plunger 113. This plunger is mounted withm thehollow 114 of the shaft 98 which supports the friction clamp 94 itself.The shaft 98 is formedas a tubular barrel having its end adjacent thehead plate 93 closed and its opposite end open. Plunger 113 is in theform of a rod projected through anopening in the closed end of the shaft98, provided adjacent thereto with a fixed collar 115 and, surroundingits body, with a spiral spring 116, borne upon the collar by a tubularadjusting plug 117 threaded into the opposite end of shaft 98, andthrough the hollow of which, in turn, the end of the plunger 113 isextended and provided with a hook 118 by means of which it may bemanually operated. The spring 116, through its engage-' ment withshoulder 115, holds the clamping jaw 111, carried at the fore end of theplunger, against the rear face of the work and presses it firmly againstthe interior faces of the jaws 104. This clamping jaw 111, like thewearing surfaces, 109 of the friction clamp (see Figs. 6 and 7), ma bemade of any suitable wearing material st'suited to the holding of thework without abrading it or marring its sharpened teeth. It also isremovable from the lunger, being threaded or otherwise remova 1y held onits fore end whereby, it, too, may be renewed upon wearing down.

The feeding mechanism F, by means of which the work so held before thegrinding tool is moved relatively thereto, comprises, as its salientelements, a feeding pawl 119 carried at the end of a feeding arm 120 onthe front face of the work below the grindin tool and intermediate thegrinding tool anthe horizontally-extending arm 45, which supports theholding and feeding mechanisms. This feeding pawl 119 is of bifurcatedform, appearing most clearly in .the semi-diagrammatic view in Fi 11. Itis comprised of a strip or rod or wire bent into substantially U-form.The bend 121' of the U is held beneath the head 121 of a clamping bolt122, secured in a supporting bracket 123 by means of wing nut 124. Theupper ends of the branches 125 of the nawl 119 are flared outwardly, andare curved toward the work as clearly appears in Figs. 1 and 2, andtheir points are not only beveled on their upper surfaces, as indicatedat 126, in Fig. 11, to sharpen their engaging ends, but these engagingends themselves are cut transversely to conform to the shape of theteeth of the work, as indicated at 127 in Fig. 11, in which the teethare curved. In the casekof straight teeth, as illustrated in the diagramin Fig. 16, these ends would appropriately be straight.

Bracket 123 is freely journaled upon a tubular ferrule 128 having a head129 on one side and projecting a distance beyond head 123 at theopposite side. The ferrule 128 is force-fitted onto the feeding arm120'so that it is normally immovable with respect thereto. Force-fittedon the extended end of the ferrule is an adjustable tension head 130,adjustable by the application of force only against. its friction holdupon the ferrule. The inner end of this head is hollowed out and withinit is mounted a spiral tension spring 131, one end of Which is engagedin the head 130 and the other end of which is engaged in the bracket121, whereby the feeding pawl 119 is borne yieldingly to the face of thework and the tension under which it is borne may be freely adjusted.

' The feeding arm 120 is L-shaped,the branch which supports the feedingpawl 119 projecting laterall below the grinding tool 49 from the right 0the machine. The main branch 132 of the arm (see Figs. 2 and 10) isrotatable and axially supported for adjustment in a boss 133 ina'bracket. 134 (see Fig. 5) 0f U-shape journaled by its arm on atransverse axis 135 (see also Fig. 5) supported there by 7 the forwardextensions 92 of the column 47. The branch 132 of the feeding arm issupported substantially from a corner of the U-shaped bracket. The bightportion of the bracket underlies the extension 92 and is providedcentrally with a depending tang 136 in which there is threaded adesignated stop. screw 137 provided with a wing jam nut 138.

The'point 'of screw 137 bears against the front ,wall of column 47 and,in accordance with its adjustment, limits the upward stroke of thefeeding pawl (see Fig. 2). Bearing upon the central portion of the bightof the U-bracket 134 from the front is a plun er 1-39 yieldingly pressedinto engagement y the spiral spring140 housed in abarrel 141 formed onthe under sideof the extension 92,'and provided with a tension adjustingscrew 142. Through the plunger 139, the feeding pawl1l9 is carriedthrough its feeding stroke by the potential energy stored in spring 140by the driving mechanism.

The driving mechanism is connected with the bracket 134 by means ofanvarm 143 depending from the bracket on the same side of the machineasthe feeding-arm 132. This arm is provided with a socket 144 onits'lower end offset laterally of itsmain body, and rethe under side ofa small bracket 147. In

the upper side of bracket 147 at right angles to the lateral side of arm145'is an elongated a pin 148 having a knurled head 149 at its forwardend and a shank 150 at its rear end,

force fitted into the tubular section 151 of a connecting rod 151, 152,extending lengthwise of the machine. Section 151 is screw threaded uponthe fore end of section 152 so that by turning the knurled head 149 ofpin 148, the aggregate length of connecting rod 151, 152 may be readilyadjusted. At its rear end, (Figs. 1, 2, 3 and 4) this connecting rod isturned inwardly of the machine b a branch 153 and, underlies the casing35 of t e driving mechanism D. Emerging on the opposite side of themachine, branch 153 is reversely turned as at 154 and its inturned end155 detachably socketed in the lower end 156 of an oscillating lever 157carried by a rock shaft 158 journaled through the. upper margin of thecover plate 36. On its inner end, this rock shaft 158 is provided with adepending cam lever 159 carrying on its lower end cam follower 160 in aposition to be engaged bycam 161 mounted upon transverse shaft 82Thereby through the reciprocation of the con identified with the drivingmechanism of the necting rod 151, 152, and the resultant feeding of pawl119, there are obtained two feeding strokes for each angular grindingstroke of the grinding tool 49. c i V The adjusting mechanism A iscomprised in considerable part of elements which have;

already figured in connection with the holdsupport of those mechanisms.Column 47 is capable of a number of adjustments with respect to theforwardly extending arm 45 upon the far end of which it is carried. Ithas already been said that it is pivotally mounted on axis 48 at theouter end of this arm. This pivotal axis is mounted across the bight 162of the hook 163 of arm 45. The body of the hook, 163, lies on the sameside of the machine as the main branch 132 of the feedin mechanismsupporting arm 132, 120.' Both the'hook 163 and the feeding mechanismarm 132 are open on the opposite side of the machine (see Figs. 2, 4 and10) whereby work may be inserted into and removed from the machinefreely from that side without havmg and feeding mechanism, especially inthe ing to thread it vertically through the body of either element.Furthermore,,work may on occasion, depending upon its shape, be the morereadily accommodated.

Column 47 is supported from axis 48 by a bracket 164 in which it isaxially disposed, and held in its adjusted position by means of a leveroperated screw 165. This bracket is provided-with a forwardly extendinglug. 166 which underlies the bight 162 of hook 163 in such manner thatthe bightconstitutes a stop limiting the extreme rearward movement ofthe column 47 about its pivotal axis 48 toward the grinding tool 49.Extending vertically through lug 166 within the bight is a springpressed L-shaped plunger 167, the horizontal branch of which engagesbight 162 on its upper side, whereby column 47, and consequently thework holder 110, are yieldingly held in the normal position relative togrinding tool 49 imposedby the engagement of stop 166 with an under sideof the bight. A knurled nut 168 provides adjustment for the spring 168'.thereby regulating the force with which the work is presented to thegrinding wheel.

Pinned or otherwise secured to the column 47 just above the top of thesupporting bracket is a. thrust collar 169. This collar is provided withright and left wings 170 in which are mounted set screws 171 whichengage opposite sides of a vertical lug 172 from the bracket 164. Sowhen the lever screw 165 (Figs. 1 and 5) is loosened, bydetting off oneset screw 171 and turning up the oposite one, column 47 may be angularlyadjusted about its axis and held fixedly in such adjusted position. Byloosening set screw 173 which holds collar 169 upon the column 47 andalso loosening lever screw 165, the col umn may be vertically adjusted.By rotating the L-shaped plunger 167 so that its overlylng branch isremoved from the bight 162 of the supporting arm, the entire holding,

feeding and adjusting mechanisms thus far described can be droppedforwardly away from grinding tool 49as shown in Fig. 1.

The supporting arm 45 is itself adjustable forward and backward withinthe offset 46 by means of which it is supported from stirrup 34 (seeFigs/2, 4 and 23, especially Fig. 2). It is not only journaled in thisboss for both axial and an ular adjustment and held normally clampetherein by a lever screw 174, but also provided at its rear end with amicrometer adjustment comprising a small pitch screw rod 176 threadedinto therear end of arm 45 and provided with a knurled head 175journaled in the opposite branch of stirrup 34 from the carrying boss46. Collar 177 prevents movement of the micrometer screw with respect tothe arm of the structure so that when the knurled head 175 supportingarm 45 is adjusted is turned, lever screw 174 beingreleased, the ymicrometer movement forward or backward as may be desired. During suchadjustment it is normally prevented from angular movement which mightturn the mechanism which it supports up side down, by means of a head178 clamped to its inner end within the body of the stirrup 34 andhaving a pair of depending'ea'rs 179, one disposed on each side of thehead of the pedestal, and each ear provided with an adjusting screw 180,all as shown in Figures 1, 2, 4 and 25.

This machine greatly facilitates the practice of my invention. very easyto practice. The file or other similar tool to be ground) is insertedinto the friction work-holding clamp 89 of the workholding mechanism Hwith its teeth pointing downward as clearly shown in Figs. 1 and 2. Itis easy to insert it, for one has merely to grasp the hook 118 and pullthe rear clamping jaw 111 away from the fore jaws 104 ..(Fig. 3) andinsert the upper end of the file between the 'jaws from the bottom.Thereupon when the hook 118 is released, jaw 111 bears frictionally onthe back of the work and holds it against the faces 109 of In fact itmakes it the fore jaws 104. In this insertion of the I work there hasbeen no interference from supporting arms 45 or from the arm 120 of thefeeding mechanism F, since the one is hook shaped as in 163 Fig. 4) andthe other is L-shaped, both open on the left hand side of the machine.So inserted the file is held by the frictional engagement of the jaws'164, 111, with the edges of the teethon its front andback. The teeth.of course, during this insertion ratchet freely past the upper end ofthe feeding pawl 119 of the mechanism F. Initially. of course, the workis hardly more than entered by its upper end in the work-holding clamp89 when the first several teeth are engaged. Thereby the ins grindingtool 49 may commence its work almost if not quite at the extreme end ofthe file. In cases where this extreme end is blank,

it is the blankend which is held by the aws 104, .111, and the grindingoperation maycommenceupon the very first tooth, there machine after thisinsertion of the work takes place as follows: The driving motor 40 bein'started. g'rindin tool 49 is rotating at big s eed through t e beltconnection 53, and is a so, at the same time, reciprocated transverselyof the machine. This 1s accomplished through the train ofinechanismincluding rack and pinions 69 and 70 and comprehending parts 1 to 88 ofthe grinding mechanism G and the' drivin mechanism D as most clearlyappears in .igs. 1, 2, 12 and 13.. At

the 'same'time the feeding mechanism F is operated at a coordinatedperiodicity by means of the train of mechanism commencing withoscillating feeding arm 120' which carries thev feeding pawl 119extending through the connecting rod 151 and ending with lever 159 andcam follower 160 (Fig. 12) actuated by cam 161 driven from the sameshaft 82 from which is driven the mechanism for reciprocating drivingtool 49 just recited. For every revolution of shaft 82 grinding tool 49is reciprocated once, by reason of the fact that'connecting rod 80 (seeFig. 12 and Fig. 1) oscillates segmental gear 76 of the train once foreach revolution of shaft 82.

But for each revolution of shaft 82 cam lever 159 is oscillate-d twiceby reason of its engagement, once by one end of the double ended cam 161of lozenge shape, and once by the other end during each revolution. Andthese engagements'are precisely 180 degrees apart. So feeding pawl 119of feeding mechanism F makes two feeding reciprocations to one feed ingreciprocation of grinding tool 49. The time is so adjusted that feedingtakes place at or near the extreme end of each stroke of the grindingwheel, while the wheel is out of engagement with the work, with theresult that the grinding tool 49 engages every other tooth on itsstrokes toward one side of the machine and thealternate teeth on itsstrokes to the opposite side of the machine, passing in its grindingoperation over each tooth during a single insertion of the work in themachine. The relative path of movement of work and the grinding tool istherefore substantially a zig zag path.

The nature of the engagement of the grinding 'tool' with the work will.be clearly apparent from a-consideration of Figs. 16 to 20. In Fig. 19is shown a length of file the teeth of which have not been ground InFig. 20 is shown a length of teeth'of which have been ground. It will beseen that the grinding operation is carried out on the margins adjacentthe edges of the teeth as indicated by numeral 181 applied to thesemarginal portions, and that the grinding does not extend all the way tothe roots of the teeth. F urthermore this margin is on the tops or outerfaces 182 of the teeth and not upon the bottoms or inner faces 183. Theteeth on most if not all straight tooth files are formed traverselyoblique to the sides of the file as clearly appears in Fig. 16 whichrepresents the same length of file as is shown in Figs. 19 and 20 infront elevation, the teeth pointing downward as in position in themachine. Here the grinding tool 49 is shown in dotted lines and its axisof rotation is shown by a dash and dot line 184. The central lane 185 ofthe grindin tool is intersected by the axis 184 at a po1nt'186 whichlies a substantial distance behind the cutting edge 187 of each toothupon the oblique outer surface. 182. The

grinding tool 49 is so disposed to the vertically extending work holder89 and the ver tieally disposed work 90 as to maintain this relation tothe parts. Furthermore the angularity of the transverse-shaft 63 '(Figs.1 and 13) is so adjusted by means of movement of frame 65 about support44 of the grinding mechanism as to insure apath of travel of thegrinding tool 49 and of its central contact with the work as defined bythe point 186 projected upon the plane of the work, substantiallyparallel to the edge of the tooth throughout both strokes of eachreciproca- 1 tion of the grinding tool 49.

So those steps of the method of my invention involving grinding to thegreatest depth at a point to the rear of the tooth edge and traversingthe point of greatest depth parallel to the tooth edge are carried out.This will be additionally apparent from the inspection of Fig. 21showing the work and a section of the grinding tool 49 in sideelevation. Here projected point 186 lies a substantial distance back ofthe cutting edge 187 of the tooth being ground andthe grinding tool isrotated to grind toward the edge of the tooth.

It will be apparent too that the plane of the grinding tool 49 lies atan angle to the cutting edge 187 of the tooth, and the line of grindingcontact, and at an acute angle a Fig. 16 disposed at an oppositeinclination to the body of the work from that of the tooth edge 187, orin the direction of said opposite inclination. By such disposi tion thegeneral inclination of the plane 185 of grinding tool 49 is maintainedat a much less value than if the grinding tool 49 were inclined in asame general direction as the tooth edges 187 with a resultant closerapproach to symmetry and smoothnessof op eration of the grindingmechanism. Through these and the former arrangements is carried out thatstep of my invention involving grinding in the path at an angle to thetooth edge, the while traversing the grinding parallel to the toothedge. Through it too iscarried out that step involving the establishmentof the greatest depth of cut in the rear of the tooth edge and carryingout the same traversing movement, and the grinding on an are shaped pathat an angle to the tooth edge and tangent the tooth edge, the curvatureof grinding tool 49 itself establishing the are shaped path and thedisposition of the grinding tool described establishing its tangency tothat line defined by the traverse of the projected point 186.

During these operations the tension of the spring 168', by means ofwhich the column 47 and consequentlythe work holding and feedingmechanisms F and H are retained in vertical position, is adjusted tosuch value full engagement, as it is when it engages between the ends ofthe teeth, forces the work and consequently the work holding and feedingmechanisms F and H ever so slightly back from the adjusted normalposition as defined by the engagement of the lug 166 j (Fig. 2) withtheunder side of the-hook 163 of the arm 45. But this movement throughcompression of spring168 is' made so slight that there remains thatdepth of cut which may be desired for each stroke of the grinding tool."To put it another way-assume the i spring 168 is adjusted to that valuewhich. will, when the grinding tool 49 is in full engagement," result inthat depth of cut desired for each stroke and also in a slight yieldingmovement of thework before the grinding tool. Theresult is the formationat each end of each tooth of a let-off 188, due to the fact thattliepressure of spring 168' when the grinding tool is entering itsengagement 7, with the tooth and before the tooth is fully in engagementtherewith is sufficient to quite overcome the less grihding pressureincident to such lesser engagement than the fuiler en- .gagement' andthereby to cause the grinding tool toe ect a deeper cut at theextremities ofthe teeth than it does at points intermediate to thepoints on the extremities, and to progressively decrease this depth ofcut to the normal as the full engagement is reached. 5

This let-off effectually precludes the extension of undesirable sharp.points at thBBX- tre'rne endsf of the tooth and eliminates theScratchings caused by each sharp points.

The'presentation of the work to the grinding tool in a position which,if not changed, will result in a depth of cut greater than desired,

,. and holding the work to the grinding tool under yielding pressureinsufficient to maintain its position before the tool when the tool isfully in engagement, and thereby .to form :teeth with a let-off at eachend is a part of my method. a During these operations the work 90 is, of

course frictionally held in the work clamp H, an jointly by reason ofthe general vertical position of this elamp, its frictional nature andthe engagement of the teeth in the feeding operation by the ends 127 ofthe feeding pawl which are disposed on the angle to the true verticalthat the tooth edges bear. to the central axis of the file (see Fig.11), the work is fed vertically .upwardialways in gravitational balanceabout its true vertical axis. More' broadly stated, the ends 127 of thefeeding pawl 119 are disposed on a line 1 bearing the same relationto'the true vertical as does the line of the tooth edge to thelongitudinal axis of the work. The work holdto ing clamp being ofafrictional nature and 'there being sufiicient play between its sidelwalls b reason of the provision of a spring 105 igs.6 and 8) to precludea guiding action b any other than the desired one of 66- these si ewalls, 105", the feeding operation itself maintains the gravitationalbalance. Thereby I am enabled to practice those steps of my mventioninvolving the maintenance of this gravitational balance of the work in avertical position to the grinding tool and to obviate entirely" allvariations whatever or defects of rinding which might result from'theintroduction of any angular gravitational components. Such eomponentswith the work fed in any other manner vary with each movement of thetool through its hold er, become reversed in sign as the workprogresses, and introduce such variations between the individual teethas to preclude that accuracy essential in files of this kind.

Moreover, in furtherance of this result I have constructed my apparatus,it will be perceived, to enable meito apply a holding pressure throughthe clamping jaws 111 and 104* symmetrically distributed with respect tothe longitudinally vertical plane. This will be clearly apparent from aninspection of Figs. 3 and 5, in which this plane has been designated bythe lines 91 and 189. There is thus no tendencypf the clamping pressure,as adjusted to most effectually coact with the feeding pawl 119 byturning up the adjusting-screw 117, to interfere with the balancingactionof this feeding pawl as the work is moved step by step forwardly.Moreover, the feeding forces themselyes, by my apparatus, aresymmetrically applied as respects this longitudinal vertical planev 189by reason of the symmetrical disposition of the arms 125 of the feedingpawl and their engagingpoints 127 as respects this plane. (See Fig.11).. This step of my method renders more'efi ectua l practice of thatstep involving the; feeding of the work in gravitational balance. I g

Of like assistance is that feature enabling me to frictionally. holdthework before the grinding tool. But this feature is of still furtheradvantage in that it enables me to hold work having teeth of differentpitch *and size without carrying out adjustments of the work holderitself. As an example, under certain conditions, unless the variationfrom the pitch in one piece of work is more than twice the pitch of theoriginal, no resetting of the feeding mechanism F is necessary. For whenthe feeding mechanism is set for a stroke substantially greater than thedistance between two. successive teeth, and stop 137 is adjusted topresent the edge of the tooth being ground in proper relation to thepath of traverse of the projected point 186, (see' Figs. 16 and 2 1); nomatter what the length of the tooth within setting of thefeedingmechanism F, the tooth edge is always presented in this samerelation to the path of travel of the projected point 186. This followsbecause, while the feeding pawl is moved on 1ts.down stroke positively,it' is moved on its up stroke by potential energy, energy Q ting of stop137 on theforward stroke.

stored in spring 140 on the back strokeand utilized to the extentdetermined by the set- So this step of holding the work frictionally ina determined area, conducting the grinding always in the central regionof this area, and

progressively shifting the clamped area from one extremity of the workto the other, and the feeding of the work through potential energenables me to maintain accurately the relation to the grinding tool andthe tooth edges and to still further increase the fineness of the workturned out.

When a piece of work is finished it is supported in the clamp 89 of thework-holding mechanism H at its extreme lower end. In this position,feedihg pawl 119 having engaged the lowermost tooth, further feedingmovement is impossible, and grinding tool 49, unless the work isimmediately removed, may engage and reengage-the next to the last tooth(since pawl 119 works within one or two teeth ofthe plane of thegrinding tool) and grinds this tooth to a slightly greater depth thanthe remaining teeth. But this is not harmful for two reasons, first,because the very limit of depth as fixed by the engagement of lug 166with thehook 163 (see Fig. 2)' of arm is not very great, being onlysufficiently greater than the body depth of grinding to insure a slightlet-0E at the ends of the tooth, so that full depth of grinding will notbe excessive. Furthermore, the sound of the machine is changed themoment grinding to a different depth occurs, and the operator maypromptly change the work.

lil)

Work is ground on one side and then tested on that side by applicationto a surface to be filed, and if insufficiently sharp by reason of beinginordinately dull, or for any other cause, the work is re-entered by itsupper end in the work holder and the same face given a second grinding,or indeed a third if that should prove necessary. The work is thenreversed and the opposite side ground.

I The adjusting mechanisms provided not only assist me in the practiceof the method of my invention, but also serve variousother ends. Themicrometer adjustment comprising elements 175, 176 etc., enables me veryaccurately. to adjust the maximum depth of cut merely by turning theknurled head 175. This produces most accurately those'minor movements ofthe work-holding mechanism H necessary for such accurate adjustment. henthe work has been finished, however, the adjustment effected through arelease of the L-shaped plunger 167, through a rotation of the plunger167, bythe knurled unit or thumb piece 168, enables me to drop theentire work-holding mechanism H forward from the position shown in Fig.2 to that shown in Fig. 1, whereby not only may the work be inserted andremoved without interference from grinding tool 49, but also anyficaciously effected through the adjustment 7 providing angularadjustment of column 47 about its axis by means of the opposed setscrews 171 in the bracket 164 which supports the column on its pivot 48.Lever screw 165 being released, one has only to let off slightly on onescrew 171 and take up-the same amount on the other, whereupon angularadjustment is fixed. That is a most important provision in that it isone of the factors insuring absolutely uniform depth of grindingthroughout the length of the tooth. At any time,

the column 47 may also be adjusted axially,

but this adjustment. is mainly for general positioning of thework-holding mechanism.

H with respect to the plane of the grinding tool such, for example, asto insure the enrespect to the path of travel of the projected 1 point186 (Figs. 16 and 21) is effected by adjustment of the stopscrew 137associated with the feeding mechanism F. The feedingmechanism Fpossesses several other adjust ments, but no others which are directedto this especial end. The adjustment provided by wing nut 124 is toenable the pawl 119 to be shifted laterally one way or the other, andenable the symmetrical application of feeding force with respect to thelongitudinal vertical planeto be maintained irrespective of the kindofwork or of the relative location of the grinding and work-holdingmechanisms. A further adjustment is provided in the variable length ofthe depending arms 143, 145. This provides principally that adjustmentrequired by vertical adjustment of column 47 Subordinately, however, itmay be used to vary the length of the stroke of the feeding pawl, andalso is a convenient means of knock down and assembly 1n case the'samelength of feeding'stroke on aw 111 irrespective of the location ofthe work-holder longitudinally of the machine.

This location is changed from'timeto time for the slmple reason that asthe grinding wheel wears, "thef-micrometer 175, 176 is adjusted nately,however, this connecting rod adjust- .ment 151, 152, does enable me tocontrol the length of stroke of feeding pawl 111 by reason of the factthat operating connection from cam 161 to cam follower 160 is a lostmotion connection, and whenrod 151, 152 is lengthened or shortened, theamount of lost motion is reduced or increased with a resulting increaseor decrease in the effective stroke of the pawl 111. By this means,therefore, I am enabled to adjust the length of stroke to work having.teeth of different pitch, as I will.

. Finally, the'innerend of thls connection 151, 152, being removablycarried in the end 156 of lever 157, (see Fig. 1), I am able, by simplyiwithdrawing it, to free the cover plate 36 and enable it to be thrownopen to disclose the interior driving mechanisms for inspection and togeneral accessibility to them.

The adjustments of the work-holding mechanism H are utilized principallyin chan ing from one kind of work to another. ere, when a batch of new vwork of different size is to be operated upon, first the work-holdingmechanism is dropped back as shown at Fig. 1, wing nuts 103 areloosened, and the fore jaws 104 are adjusted approximately to the widthof the inserted work, so that one side bears against and is guided bythe side wall 105-13 of'one jaw 104. The other side is borne uponyieldingly by the spring 105a. Then wing nuts 103 are tightened up.Loosenin thumb screw 102,- the work holder 89 is a justed bodily uponthe shaft 98 until the pressure exerted by the back jaw 93 is adjudgedto give that (approximately) degree of friction clamping desired.Thereupon the column 47 is swung to its vertical position, as shown inFig. 2, and in this position thethumb screw 100 is loosened and the workholder 89 adjusted toward or from the tion of shaft 98 in boss 99. Andwhen in pobe attained.

sition, the single thumbscrew 100 retains the parts in position asagainst both of these adexact gravitational balance and precise symmetryof work holding'and grinding process is assured is carried out by meansof opposed adjusting screws 180 in the ears 179 of the adjusting head178 on the main supporting arm 45 (see Figs. .2 and 25). Lever screw 174being temporarily released letting off on one. screw 180 and taking upcorrespondingly on the other a fraction of a turn, enables a very fineadjustment to be made, and a substantially perfect balance anddistribution to The adjustments of the grinding mechanism G have alreadybeen described, except those adjustments which pertain to accessibility.The guide 63 is circular in crosssection and constitutes additionally ahinge pin 191 offthe frame 65. But one ear 190 may be removed to swingthe grinding wheel downwardly from frame 65 through movement of thegrinding wheel to an inordinate extreme position, as may be done eitherby disconnecting the connecting rod 80 (Fig. 12), or by swinging cover36 outwardly, which of course disengages from worm gear 84. On its innerface, opposite the plane of the inner face of the frame 65, the bracket62 carries the feltlined lubricating channel 192 which lubricates thefaces of the two brackets as the reciprocate in sliding engagement.

Not only is my invent-ion adapted to grind straight toothed files ofvarious shapes, but it is also adapted to grind curved toothed files ofvarious shapes. A curved tooth file. is shown in semi-diagrammatic viewin Fig. 11. Here, the ends 127 of the pawl 119, when at the upper end ofits feed stroke, lie on the are 193 of a circle struck from the center194 of the driving shaft 71 of the grinding mechanism. They lie, too, onthe arc of the arc-shaped tooth root beneath which they engage, this arebeing struck. from the tooth center 195' located on the verticalgravitational axis 91 of the work (or some other line common to all theteeth). So, the file with curved teeth may be fed according to themethod of my invention also in gravitational balance.

. In this grinding of curved teeth I use a.

I modified form of grinding mechanism G,

.inserting it's shaft 71 through the bracket 4.4

and replacing the gear 72. This mechanism consists of a bracket 195fixed to the shaft 71 and carrying a fore extension 196 adjustablyclamped to its under side and carrying the grinding tool 49 in adepending position by. means of a collar 60, and a bearing column 50 anda shaft 51 in all essential respects like the parts of similar numberin.

the othermechanism. By reason of the fixed connection of the supportingbrackets 60' to the oscillatingshaft 71, when this shaft is oscillated,thegrinding tool 49 is oscillated, but instead of reciprocating on astraight line path, it oscillates on a curved path of'a radius of thedistance of the plane of the grinding "tool 49 below the axis of theoscillating shaft 71.- This distance is adjusted by adjustment of thebearing column in the bracket 196-to make the radius of oscillationequal to the radius of the curved teeth of the file being ground. It -isthe radius R in Figure 11. The grinding .wheel is shown in this figurein dotted lines in engagement with the tooth at the end of this radius.The angularity of the plane ofthe grinding tool with respect to theradius R i's'adjusted so that the same' conditions of location of thepoint of greatest depth 186 and-its path of travel with respect to thetoothed edge, parallel to that edge and removed a distance back of it,and the same conditions of angularity of the plane of the grinding Wheel'with respect to the edge of the tooth, and all the other outlinedconditions, pertainhe're in'just the same manner in which they pertainin connection with the grinding of straight teeth. And .since thefeeding pawl 119 needs engage below the tooth being ground by one or twoteeth, the radius R, defining the are 193, is greater than the radius R,and the points 127 of the branches of the pawl lie at the point ofintersection 0am 193 with the arc of the tooth engaged by the pawls.Thus with the substitution of the oscillatable grinding mechanism G forthe reciprocable grinding mechanism G, and the adjustment'of the pawl119, the

' method of my invention may be practiced as fully and completely uponfiles with curved teeth as upon files with straight teeth.-

.' Reverting to the gearing shown in Fig. 12 for the oscillating of thegrinding wheel 49 and of the movement ofthe feeding pawl 119, it may besaid that Fig. 22 shows in transverse section the cam 81, its mountingon the *2 cover plate 36, and its removable coupling in' gravitationalbalance may be substantially wholly by the vertica disposi-- with theworm gear 83. This removable coupling is by means of flat headed pin 196screw threaded into the cam and securing the connecting rod thereon. Thefiat head is entered into a slot 197 formed in the outer face of theworm gear 83. Thereby when the cover plate 36 is swung on its hinges,cam 81 is at once, uncoupled by the movement of the flat head 196' outof its slot 197. Thereupon the grinding mechanism may befreelyoscillated and adjusted, and the feeding.

mechanism may be operated, all by hand, to place everything in workingorder before turning on the power.

A stub shaft 82 is carried in the boss 198 ofthe hinged'side 36 of thecasing 35 by means of a bearing sleeve 199 having a force fit therein.Stub shaft is retained in the sleeve by the knurled head 200 clamped onits outer end, and by means of which the grinding and feeding mechanismsmay be manually operated- Lubrication is by means of 011 holes 201normally closed by a spring ring 202.

Referring to Fig. 23, it will be seen that the micrometer shaft 176 isretained in place by a bearing of an inside collar 177 and a head 175,respectively, upon the opposite ends of a bearing sleeve 203. Thissleeve is .of.slightly larger diameter than each the collar 177 and thehead 175, and is held inplace within the bore 204 in the vertical branchof the stirrup 34 by means of the set screws 205. By simply removin theset screws this entire micrometer ad ustment may be removed in entirety,along with the shaft whenever desired.

Too, it should be noted that Figs. 6 and 8 pertain particularly to theholding clamp adapted to hold in place straight toothed files. Thesefiles usually have parallel side edges, and the right hand edge is heldfirmly up against the extended guide 105-'B connected with the righthand jaw 104by the .pressure of the steel. spring 105A.

With proper relation ofthe guide 105B and the pressure of spring -105-A,as adjusted by the movement of the jaws 104 toward each other,.themaintenance of the file reserved tion of the ide 105B against which itsedge bears uring the entire feeding movement. In such case I have used,and in some cases prefer to use, a feeding pawl having but a singleprong 125 instead of a double .just the feeding pawl by means of the adjustment 124 provided as to locate the single feeding pawl on thegravitational axis llne 91 (see Fig. 11) and thereby'avoid dissymmetryof application of the feeding force which might tend todisturb in anyway the continuing'gravitationai balance of the file against thestraight edge 105-43.

Figs. 7 and 9 pertain particularly to the holding and feeding ot thecurved tooth files shown in diagram in Figs. '11 and .18. In this case,owing to the fact that the teeth are curved, and the fact that a veryprecise lateral adjustment of the file would have to be carried out ineach case in order to insure a grinding parallel at all times to the areshaped edges of the teeth, and owing to the furtherfact that even aslight variation in the width of the file, or any parallelism betweenits ofiset sides, would result in a variance from this essentialparallelism of the arcs of grinding and arcs of the edges of the teeth,I prefer to employ the double pointed pawl 125 illustrated in Fig, 11,and to adhere to the location of this point at the point of intersectionof the radius Rf;

and R of the engaged tooth edge, respectively., :I prefer, too, not touse a guide 105-B or even a 5 ring 105 -A, but, instead, to provide theaws 104 with the wearing workifaces 1 09, and to so: adjust them thatthere is a clearance on each side of the work, as indicated inFig. 11,whereby the work automatically adjusts itself about the points 127, thepoints 127 defining accurately the 'positiorr of the arc shaped edges ofthe teeth with respect to the path of rinding, and retaining thisdefinition t roughout the feeding Toperation. The

. K slight play necessary to insure this automatic perfection of theadjustment is insuficient to an extent sufiicient to enable the grindingotherwise, the,

wheel 49 to engage the work freely in a path directly opposite theclamping jaw 111, and approximately centrally of the clamp itselfwhereby the ap lication of the friction clamping force and t e grindingare both carried eut symmetrically with respect to the central axis ofthe clamp; or, stated inding is carried out about thecentral axis beforeapplication of the clamping friction. The slot designated 206' is in theone case curved and in the other case straight, according to the shapeof the path of" movement of the grinding wheel.

'Too, it? should be noted, in closing, that there is especial merit inthat feature of my method according to which the file is operated onfrom a top end down, being engaged first at its top end and fedvertically upward.

Not: only is the gravitational balance the more quickly and eifectivelyestablished, and the grmding operation started off in perfect alignmentand adjustment, but also any foreign matters between the teeth arepromptly dropped since the teeth are pointing downwardly, all dust isprevented from lodgment in the teeth, the teeth more effectively engagethe faces of the clamp and hold the work firmly sustained from itsfrictional engaging faces much more effectively than if the teeth werepointing up, and they might slip: freely past the engaging surfaceswithout biting into them, and, finally, the entire organization of themachine is rendered decidedly more practical since the main bodies ofall of the mechanisms can be located nearer the base of the machine,giving a low center of gravity, and since, when the grindingoperationtakes place at the top of the machine, the

operation and all of the immediately associated mechanisms is. the moreopen for ful inspection and adjustment.

There are, as usual, advantages of my in 'vention which I have not takenthe opportun:

ity to mention'for the sake ofv brevity, and still others which are soobvious asfnot to need mention. The outstanding advantages are so great,however, as to ma e going into the auxiliary or lesser advantages oflittle moment in connection with the exposition of the method at large,and this preferred form of machine for carrying it out. The machine hasproven so very useful and the work of such a high order and the savingof file renewals, through its use, so great that it; is probable anunusual number of ways and means may be 'devised to modify it to meetspecial conditions, or to meet competition, and for various otherunusual ends. Without doubt the invention is susceptible of a largenumber of modifications with the same and perhaps with attendantadvantages. All modifications not diverging from the generic: spirit ofmy invention I shall endeavor to cover in the annexed claims.Particularly do I wish it understood that while I hate described andclaimed my invention with particular reference to file grinding,theapplicability of the prior art as respects machines for grinding toothedwork of other'description and of a great variety indicates it isprobably applicable in some phases to the grinding of other varieties oftoothed work. The claims should, therefore, not be limited by theircircumstantial terminology to the application of .the invention to thegrinding of files, except in so far as the prior art anticipates thegeneric spirit of the invention. I

I claim: L1. The method of grinding files having non-rectilinear edgeswhich consists maintaining the filevertically in gravitational balancebefore the grinding tool throughout grinding member.

the grinding operation, and avoiding general lateral guiding.

2. The method of grindingfiles having a substantial axis of symmetrywhich consists in maintaining the article before the grinding toolgravitationally balanced vertically about said axis of symmetry,applying 'a feeding force substantially parallel to said axis andsymmetrically distributed with respect thereto, and avoiding generallateral guiding.

3. A file grinding machine comprising a grinding tool, a friction clamparranged to hold the'work before saidtool, a feeding member adapted toengage the teeth of the work and feed it forward through the holderwhich feeding member has a reciprocatory movement comprising forward andback strokes, positive means for carrying the feeding member throughvariable back strokes of alength unequal to the distance between teeth,and impositive means for carrying the feeding member through its forwardstrokes, together with means fixing in space the end of the forwardstroke of said member, the grinding tool being arranged to operate upona-file tooth directly engaged by the feeding means.

4. A file grinding machine comprising a grinding tool, a friction clampwork holder to hold the work before the tool, a reciprocable feedingmember to carry the work forward tooth by tooth through said frictionholder, a stop establishing a fixed point for the extreme forwardmovement of said feeding member, positive driving means for said feedingmember on its back stroke and impositive' driving means therefor on itsforward stroke, the grinding tool being arranged to operate upon a filetooth directly engagedby the feeding means.

'5. A machine for grinding files comprising a trav'ersable grindingmember and a 'universally adjustably supported file-supporting member,means for traversing said grinding member, means for obtaining rough andfine adjustment of said supporting member in various directions, andpower operated means adaptable to said adjustment forfeeding a filetooth by tooth through said supporting member at each traverse of said6. A machine for grinding files comprising a" clamping member forfrictionally holding a file and a grinding member traversable .yrelativethereto, means for causing traverse of said grinding member, means forfeeding a file through said clamping member relatively to said grindingmember, said means being operatively supported in a casing car- ..ryingsaid grinding member, part of said means being carried on a hinged coverof said casing. Y

7. In a file grinding machine comprising a traversable rotaryfgrindinmember and a clamping member for frictlonall-y retaining a file to .beground, common means for traversing said grinding 'member and forfeeding said file through said clamping member to present successiveteeth to said-grinding member, said means being normally 'actuated bymeans which drive said rotary grinding member, but disconnectibletheretoothat each traverse of said wheel thereover, both of said meansand the wheel being actuated from a common source.

9. In a machine for grinding flat faced milled files, means to support afiat face of a file to be ground in a determined plane, a grinding wheeloscillatable about an axis transverse to said plane with the peripheryof-the grinding wheel tangent to said Plane, means to relatively feedthe support and the wheel, and means to relatively adjust both tlllesupport and the axis parallel to said ane. p 10. In a machine forgrinding flat faced milled files, a grinding wheel reciprocable parallelto a determinate plane which is tangent to the periphery of the grindingwheel,

and on a determinate path, means to support vthe flat face of a file tobe ground in said and on a determinate path, means permanently securedto the machine to support a file with its face in said plane, means torelatively feed the support and the wheel, and means to relativelylaterally adjust said support and path of movement with respect to eachother parallel to said plane without disturbing the permanent securementof the support to the machine.

12. In a machine for grinding fiat faced milled files, a grinding wheelreciprocable parallel to a determinate plane which is tangent to theperiphery of the grinding wheel and on a determinate path of tangency,means to support a file with its face in said plane, a feeding devicefor feeding the file, and means to relatively laterally ad-'

